The present invention relates to an apparatus for magnetic digital data recording and playback and, more particularly, to a circuit for equalizing the waveform of a signal which is reproduced from a magnetic recording medium by such an apparatus.
In a recording and playback apparatus of the type described, a magnetic head reproduces a binary coded digital signal from a magnetic tape and feeds the digital signal to a waveform equalizer circuit via an amplifier. The equalizer circuit serves to compensate for the attenuation of high frequency components of the signal which occurs during recording or playback operation. For the compensation, the equalizer circuit removes a skirt portion of the waveform of the input signal thereby preparing a so-called "thinned" signal waveform.
Thinning a signal waveform at the equalizer circuit is effective to suppress interference between waveforms and, therefore, the interference attributable to a decrease in the interval between successive magnetic flux reversals which reduces the margin available for signal detection.
Such a waveform equalizer, however, cannot be constructed to thin a signal beyond a generally accepted limit. Should the input signal be thinned to 60% of the half power width of a solitary waveform in an input signal, the peak level would be lowered by approximately 40%. Thinning an input signal beyond this ratio is difficult and, rather, results in an insufficient performance, i.e., merely serves to lower the peak levels of solitary waveforms. Furthermore, the waveform in this situation will become compensated to such an excessive degree that develops undesirable false peaks.